Large quantities of water are produced during oil and gas operations. For example, 2.2 cubic meters of waste water (on average) can be generated per 1 barrel of oil extracted during oil sands mining operations. In some cases, the waste water can contain 30 weight % or more of suspended solids known as “tailings.” The tailings can consist of water, silt and clays which can become mature fine tailings (MFT) over time.
The mature fine tailings can remain suspended in a tailings disposal pond because of the low sedimentation/consolidation rate, and can precipitate out over a prolonged period of time (sometimes up to 30 years). This can have a significant negative environmental impact, as the land under tailings ponds cannot be reclaimed for several decades. Also, water from tailing ponds cannot be recycled due to the presence of stable fine particles.
Chemical aids such as flocculents and coagulants have been widely employed in order to reduce settling time for solids in tailing ponds. However, these chemical aids only reduce settling time by a marginal amount (to approximately 10 years) and may change the chemical composition of treated water. It is desired to further reduce settling time and minimize environmental impact from oil sands mining operations. Thus, improvements in this field of technology are desired.